PROJECT SUMMARY In 2016 an estimated 1.2 million children were born to HIV-infected women in PEPFAR-priority countries alone, and most pregnant women are now on lifelong antiretroviral therapy (ART). However, nearly a third of these women have detectable viral load (VL) during pregnancy or postpartum. While VL monitoring is recommended worldwide, its scale-up lags behind in many settings. Further compounding the issue of inadequate VL monitoring is the inability to monitor appropriately for HIV drug resistance mutations (DRMs), which are increasing in resource-limited settings at an alarming rate. Point-of-care (POC) VL assessments are feasible, accurate, and potentially less expensive than laboratory-based assays and may facilitate more timely viral suppression by providing rapid return of results. In addition, a POC DRM assay could significantly overcome current barriers in DRM monitoring, and extend longevity of 1st and 2nd line ART regimens. Coupling POC DRM monitoring with a POC VL testing strategy brings together two powerful innovations that could revolutionize HIV treatment monitoring. Collaborators on this proposal have developed a novel, inexpensive POC DRM assay named OLA Simple. In the proposed study, we will validate the OLA Simple by leveraging an existing CFAR-funded study, Optimizing viral suppression for pregnant and postpartum women living with HIV through point-of-care viral load testing (Opt4Mamas). Opt4Mamas is a prospective, interventional study evaluating the effectiveness of a POC VL testing algorithm on viral suppression rates among 700 pregnant and postpartum women on ART in Kenya. Layering on the existing aims of the Opt4Mamas study, we propose validating OLA Simple against gold standard DRM testing (Aim 1), evaluating OLA Simple's usability and costs (Aim 2), and determining patterns and correlates of pretreatment and acquired DRMs (Aim 3). This study is a critical first step in optimizing VL and DRM testing to maximize viral suppression among pregnant women and, in the near term, directly informs national policy approaches to HIV treatment monitoring among pregnant women in Kenya. It also serves to generate preliminary data for an interventional R01 study testing the clinical benefits of combined POC VL and POC DRM testing. This proposal ultimately addresses the urgent need to find interventions to maximize viral suppression among pregnant women on ART, eliminate MTCT, and achieve the UNAIDS 90-90-90 goals.